entitled "Piping" in this section and other items required for a complete,
operable, pneumatic system.
2.12.12
Primary Ash Receiver-Separator and Secondary Ash Separator
Provide on top of ash silo two stages of receiving and separating, with
each stage a complete self-contained unit with efficient dust and air
separation and gravity dump bottom gates to open with interruption of
vacuum and discharge into a silo. Design system so that suction is
positively shut off from the receiver during its dumping period, so that no
dust can be sucked out through the exhaust while the discharge of the
receiver is open or opening.
Air from the primary receiver shall enter
the external secondary separator which shall remove approximately 85
percent of the dust not collected by the primary receiver. Combined
efficiency of the primary and external secondary separators shall be not
less than 95 percent. Provide completely contained gate assemblies in a
dust-tight enclosure fitted with access doors large enough to remove entire
gate assembly. Provide receivers of hard, abrasion-resistant, cast alloy
iron with a Brinell hardness of not less than 500 constructed as described
below:
2.12.12.1
Primary Receiver-Separator
Not less than [914] [1219] mm [36] [48] inches inside diameter with cast
sections 19 mm 3/4 inch thick and 50 mm 2 inch thick impingement section.
Cylinder, along with the discharge hopper shall be of segmental bolted
construction. Construct receiver to ensure dropping of the maximum
quantity of solids from the transporting air. Provide carbon steel outlet
pipe and discharge gate. Receiver-separator shall have an internal baffle
assembly to prevent re-entrainment of ash.
2.12.12.2
Secondary Separator
Not less than [406] [508] [610] mm [16] [20] [24] inches inside diameter of
not less than 8 mm 5/16 inch thick one piece construction with at least 13
mm 1/2 inch thick inlet wear section.
Design the receiver to minimize the
carry-over of fly ash into the [air washer] [tertiary bag filter].
Separator shall have an internal baffle assembly to prevent re-entrainment
of ash once it has fallen into the collection hopper of the separator.
2.12.12.3
Dust Tight Enclosure
Support primary and secondary receivers on not less than 6 mm 1/4 inch
thick, dust tight, carbon steel support boxes with hinged access doors or
removable panels on each side for servicing the receiver swing gates.
Provide support box with airtight roller bearings, hinged, counterweighted
swing gates with removable neoprene seals. Gates may, as an option, be air
cylinder operated gates in lieu of the counterweighted gates.
2.12.13
Mechanical Exhausters
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NOTE: When environmental restraints, availability
of steam or water or economics preclude the use of
steam exhausters, use a mechanical (electrical
driven) exhauster with a pulse jet bag filter to
produce the required system air flow.
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SECTION 15502N
Page 134
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